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Heterogeneous genetic variancias geneticas heterogeneas em rebanhos simulados fechados sob selecao
Assuming that selection in closed herds can promote reduction in additive genetic variance, multiple regression models were used to estimate this change in additive genetic (co)variance component, over the years when the selection was done. Weights at 550 days (W550) were studied using simulated dat...
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Published in: | Acta scientiarum. Animal sciences 2012-01, Vol.34 (1), p.83 |
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Main Authors: | , , , , , |
Format: | Article |
Language: | Spanish |
Subjects: | |
Online Access: | Get full text |
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Summary: | Assuming that selection in closed herds can promote reduction in additive genetic variance, multiple regression models were used to estimate this change in additive genetic (co)variance component, over the years when the selection was done. Weights at 550 days (W550) were studied using simulated data of herds submitted to 20 years of selection. (Co)variance components were estimated assuming that the weight at 550 days was a new trait every five years, by multiple-trait analyses involving four traits in the animal model. Three multiple regression equations were fitted--RMI, RMM, RMF--estimating thus the additive genetic (co)variance components for the 20 years of selection and eight years prior to the selection process. The initial years of each generation of selection were used as a covariate in the RMI. In the RMM, intermediate years were used, and the final years were considered in the RMF. The equations showed high coefficients of determination. However, there was no difference in the adjustment between the models. It was observed that the multiple regression models can be used in the estimation of genetic (co)variance components, when heteroscedasticity is assumed over time due to the selection process. Keywords: (co)variance components, heteroscedasticity, Bayesian inference, multiple regression. Assumindo que a selecao em rebanhos fechados pode promover a reducao da variancia genetica aditiva, foi estudada a possibilidade do uso de um modelo de regressao multipla para estimar os componentes de (co)variancia genetica aditiva, ao longo dos anos em que a selecao foi praticada. Foram utilizados dados simulados de peso aos 550 dias em dez rebanhos de bovinos de corte submetidos a selecao por 20 anos. Assumindo que a cada cinco anos o peso aos 550 dias era uma nova caracteristica, por meio de analises multicarater envolvendo quatro caracteristicas, em um modelo animal, foram estimados componentes de (co)variancia. Foram ajustadas tres equacoes de regressao multipla, RMI, RMM, RMF, estimando componentes de (co)variancia genetica aditiva para 20 anos de selecao e para oito anos anteriores a selecao. Na RMI, foram utilizados os anos iniciais de cada geracao de selecao, para a RMM os anos intermediarios e na RMF os anos finais como covariavel. As equacoes apresentaram altos coeficientes de determinacao, no entanto, nao houve diferenca de ajuste entre os tres modelos. Observou-se que os modelos de regressao multipla podem ser usados na estimacao dos componente |
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ISSN: | 1806-2636 |
DOI: | 10.4025/actascianimsci.v34i1.10934 |